You can enable the history plugin, which saves all logs to ~/.kde/share/apps/kopete/logs/username.xml
On the otherhand, this is a little rash though, you can set up an action to log on message received in the kopete notification dialogue(Settings -> Configure Kopete -> Behavior -> Configure Sounds & Events). Note that this does not discriminate against users, it appends to the end of a text file.
Can't help you with the importing though.